Издательство: | Книга по требованию |
Дата выхода: | июль 2011 |
ISBN: | 978-6-1312-3151-3 |
Объём: | 84 страниц |
Масса: | 147 г |
Размеры(В x Ш x Т), см: | 23 x 16 x 1 |
High Quality Content by WIKIPEDIA articles! In mathematics, a transitive dependency is a functional dependency which holds by virtue of transitivity. A transitive dependency can occur only in a relation that has three or more attributes. Let A, B, and C designate three distinct attributes (or distinct collections of attributes) in the relation.Another way to look at it is a bit like a stepping stone across a river. If we consider a relation to be our river with a primary key A to be the far bank of the river and our non-key attribute C to be our current location, in order to get to A, our primary key, we need to step on a stepping stone B, another non-key attribute, to help us get there. Of course we could jump directly from C to A, but it is easier, and we are less likely to fall in, if we use our stepping stone B.
Данное издание не является оригинальным. Книга печатается по технологии принт-он-деманд после получения заказа.